Figure 2. Vaccination of chickens.

Groups of 10 SPF chickens were immunized with 10⁷ TCID₅₀ of NDV-H5 or NDV-sH5³, either via the ON/IT or IM route. Another group received an IM immunization with sH5³ adjuvanted in Stimune. As a challenge control, one group of chickens was mock-vaccinated with PBS. Three weeks after the vaccination, birds were challenged with ∼10⁵ TCID₅₀ of HPAIV H5N1. A and B) Kaplan-Meier survival curves indicating percentage of survival p.c. on each day for each group that was (mock-)vaccinated via the ON/IT (A) or IM (B) route. C and D) Clinical index calculated on basis of clinical signs (as described in materials and methods) observed after challenge for each group that was (mock-)vaccinated ON/IT (C) or IM (D). An index of 3.0 means that all birds died within 24 hours. For reference, each panel includes the same PBS group.